This invention relates generally to the field of optical instruments, and more particularly relates to reflective telescopic and imaging systems. Such instruments are used, for example, in earth resources surveys made from high altitude vehicles and satellites using radiation in the ultraviolet, visible, and infrared bands of wavelengths.
In order to be useful, such surveys must cover a relatively wide field of view in at least one direction with relatively high resolution. In such a system, the vehicle is moved in a direction perpendicular to the direction of wide-field view in order to cover an area to be observed. Alternatively, a scan mirror within the vehicle may be used to achieve similar results.
In satellite systems, monochromatic defects must be minimized and chromatic aberrations must be avoided. Moreover, such systems must have broad spectrum coverage and image quality independent of wavelength. The entire system must be well suited to extreme environmental conditions, such as mechanical shock, thermal expansion and humidity. The optical system also must exhibit low scattering of incident radiation and must eliminate diffracted radiation from points outside of the field of view, which is important for background discrimination. This combination of restraints presents a very difficult overall problem which the present invention was designed to solve.